Method and apparatus for separating vapors and gases



W. A. PATRICK, B. F. LOVELACE AND E. B. MILLER.

METHOD AND APPARATUS FOR SEPARATING VAPORS AND GASES.

APPLICATION FILED 050.28.1918.

1,335,348, Patented Mir. 30,1920.

2 SHEETS-SHEET Z- "On/5.55M 44%. 6 5% W I I UNITED STATES wAL'rEa A.. ra'rmex, BENJAMIN E. LOVELACE, ANl) EaNEsr n. MILLER, MARYLAND. v a

PATENT OFFICE.

or BAL'rmoaE,

METHOD AN APPARATUS FOR SEPARATING VAPOBS AND GASES.

Specification 'of Letters Patent.

Patented Mar. 30, 1920.

-'App1ioation filed December 28. 1918. Serial No. 268,710.

To all whom itma concern:

Be it known that we, WALTER A. PAT-- RICK, BENJAMIN F. LOVELACE, and ERNEST B. MILIiER, citizens of the United States, and residing at Baltimore city, Maryland, have invented certain new and useful Improvements in Methods and Ap aratus for eparating. Vapors and Gases, 0 .which the following is a specification.

In industrial processes it is frequently necessary or desirable to separate a gas or vapor from a mixture of gases or vapors.

This separation may be, primarily, for the purpose of recovering an utilizing a valuable constituent in. the mixture, or it may be merely to-remove an impurlty.

adsorbed gas gas exteriorly thereo The present invention aims to provide a method of separating or recovering a gas gases or vapors or both which eliminates the difliculties andlimitations of previous methods, whereb the gas or vapor, even when very dilute ma be .recovered at moderete temperatures an pressure.

Briefly stated, the invention consists in passing the mixture of gases or vapors at a moderate temperature and pressure into a gel having pores of a proper size wherein the selected gas or vapor is adsorbed out of the mixture and then recovering the adsorbed gas or vapor by disturbing the equilibrium etween the adsorbed as in the gel and the In some cases the ture of gases prior to being passed into the gel may be cooled.

It has long been-known that a fine porous structure is demanded in order to efficiently adsorb fluids but, so far as we are aware, no one has discovered that the size of the pores also controls the liberation or recovcry of the adsorbed fluid. This discoveryiorms an important' feature of our invenour method preftion. The gel employed in eralzly has; pores ofsuch size that the select gas is adsorbed at a relatively high temperature,

but the pores are .not so 'sma as to render the recovery or liberation of the diflicult or impossible. The.

res of a'gel are so small that it is a very difiicult matter to accurately determine their size. However, for the pn .of defining the size of the pores requ re sure of about 12.5 mm. ofmercury,

4 contrary, we 'preferabl employ a y uniform size, but

per limit mentioned abo gels having pores of of gels of this in a gel adapted for nse' inpractising our method, the ef- V ressure of water adsorbed feet on the vapor ord a sufiiciently accurate by the gel will a method of expressing their size and this" method will now be described.

. It is a well known'fact that liquids, pro- -,vided they wet the surrounding, surfaces,

have a lower vapor pressure in small capil- The lowering of the vapor pressure by the liquid within the ca illary tube is not appreciable until the 'ameter of the tube is extremely small. For example, it has been shown that water at 15 C, has a vapor preswhile in a tube of .000005 mm. diameter, the vapor pressure is approximately 6.0 mm. When a gel adsorbs water the first cpllantities are taken up under low pressure w finally a point is reached where large amounts are taken up at substantially constant pressure. The gel or dium employed in our method has pores of such 'size as .togive a vapor pressure of water at 15C. of from 3'to 11 mm..of mercury when the adsorption of the water has reached the mentioned above. It is' to be understood does not mean that any one gel must have pores of various sizes rang: ing between-the limits mentioned. On the gel having res of substantia as will appear hereinafter, the adsorption of certain gases or vapors will be eifected more efliciently with a gel having small :pores than one having pores We have found that a size withinthe limits mentioned not only exhibit the adsorptivepower characteristic general character butat the same time permit easy liberation of the adsorbed gas or va r. Gels having ,larger ll pores have so littejad sorptive power as having be .valueless commercially." Those smaller pores have high adsorptive power but will retain the adsorbed material so sfitrelngly. as to make liberation thereof dif- A gel prepared by theooagulation'of a ich increases until" adsorbing meapproaching the up- .l'ary tubes than they do in larger vessels.

constant pressure phase' collodial solution of silicic acid, thoroughly. washed an'dldried in a suitable manner to give a product containing a small amount of water of hydration, has pores of a size gels having a proper structure might be used, For example, the gelsof alumina, ferric oxid, stannic'oxid and-others, may be I 7 prepared so as'to satisfy the conditions in regard to the size of the pores.

From the foregoing it will be apparent that in the present method, advantage is taken of the effect which small capillaries have upon the vapor pressure of a liquid. A condensation of the gas or vapor similar to liquefaction is brought about in the small pores of the gel. molecules are crowded together in-t-he small interior spaces of the gel to such an extent that, so far as the quantity of matter perunit volume is concerned, the state of the adsorbed material seems to resemble more closely the condition of a liquid than that of a gas. In fact, the evidence seems to indicate that under certain conditions, the gas is actually liquefied in the pores. These effects are obtained under conditions of temperature and pressure widely different from .those' under which ordinary liquefaction takes place. This in order to liquefy sulfur dioxid out of a mixture containing-1% sulfur dioxid and 99% air and working at a temperature of '0?- ccntigrade a pressure is required of the order of magnitude of 100 or 200 atmospheres. If, however, we cause a similar mixture containing even less sulfur dioxid, say 0.5% sulfur dioxid at a pressure ofone atmosphere to pass through a el of slhcic acid 0 centigrade, the sulfur ioxi'd Will be practically completely. adsorbed for acertain time and this adsorption will take place quite rapidly. For example, if we use 20 grams ofgel and the above described mixture is passed through the same at the rate of 400 cubic centimeters per' mimae,"

only a trace of sulfur dioxid will be present in the exit gases during the first two or three hours. At about this time a detectable amount of sulfur dioxid to come through, the amount increas ng with the time I a I a The amount of sulfur dioxid that will be adsorbed for a unit weight; ofglel is'a the adsorpamount of sulfur dioxid taken in by the gel increases as the temperature is lowered of 0.5% the gel-butthe gel ismaintained at 5 centior the concentration increased.--- Thus, if as before,

mixture ispassed into 20 grams of That is to say, the gas .400 cubic centimeters -per minute' de instead of 0 centigrade the eriod 5:21- which 100% adsorption is obtaine d will be shortened. If the operation is carried on at 10 centigrade the period of 100% adsorption will be slightly shorter and at 20 centigrade the period will be still shorter. With higher percentages of sulfur dioxid the period over which 100% adsorption 'is obtained will be less than for a 0.5% mixmm; but the total amount of gas present in the gel at the end of the. period of 100% adsorption will be' greater. Stated in other w0rds, if a given mixture of S0,, and air is passed over a gel maintained at a'given temperature, adsorption will continue to take place until a de'finite amount of SO has been adsorbed. Beyond this point no further adsorption will take place, the concentration of the exit gases being the same as that of the entering gases.- If an air mixture containing a higher concentration of S0 is now passed over the gel, further concentration will take place up to a certain ppint when the adsorption will again cease. n the other hand, if, having saturated the.

' el at,a iven tem erature with reference to a particular concentration of S0 a mixture containing less S0, is passed over the gel, the gel will give off SQ for awhile, but ultimately a condition of equilibrium will be established, that is, the concentration of the exitgases will be the same asthe entering gases. a Stated in general terms, at a given temperature the gel containing-a definite a-monnt of adsorbed SO, will be in equilibrium with gases exteriorly thereof if the concentra: tionof SO in said exterior (ses is the I proper amount; and either a sorptlon or liberation will take place if the equilibrium 'with lowering of temperature. In practice, as a general rule, we accordingly adsorb a given vapor at as lowa temperature as can 1 be economicallymaintainedr For a vapor 'which, in the liquid condition, bOllSJlIldGl' atmospheric pressure at approximately 0 0., adsorption may take place at any tem erature up to about plus 30- C. or, & 0 i or efi'ective' adsorption of gases which m the liquid condition have lower boiling points, as carbon dioxid, forexample, correspondin 1y" lower item eratures are neces.

or the adsorptlon of vapors of liq.-

uids withfhigher-bofling. points, aslether, acetone, gasoline, etc, there is a-much wider .range of temperature which may beipra'ctically realizable and over which 'efi'ective adsorption willxtalreplace; ordinary temperatures. (20 C. to 30 C.) very eflicientadsorption of substances of this type occurs. In so far as a rule can be fo1.mu,-,;j lated which will apply to gases and vapors.- in general, it may be said that, in. practice, adsorption may take place either below or not more than about 50 above the temperature at which the liquefied gas boils under a pressure of one atmosphere.

3 Another important feature of our invent1on which we desire to emphasize is that a el having a structure similar to that of sil- 1ca gel may be made to give off the adsorbed gas or vapor at "a temperature not very dif- 15 ferent from the temperature at which the adsorption takes place. Thususing silica gel, orother gel of similar structure, sulfur dioxidmay be adsorbed from a mixture con-. taining less than 1% sulfur dioxid at centigrade or centigrade and liberated at 100 centigrade eithenin practically pure condition or admixed with air up to nearl- 100% sulfur dioxid. Thus if the gel whic has been saturated with SO by passing over it a 0.5% mixture of SO and-air at 10 centigrade be maintained at 100 centigrade and a stream of air be sent through it at atmospheri pressure, by r lating the amount of air fed, any desire mixture up to about 25% sulfur dioxid by volume maybe obtained. Again, the adsorbed sulfur d1- oxid maybe liberated by air at atmospheric pressure and at a higher temperature, therey obtaining a higher percentage of sulfur dloxid in the mixturerecovered. Another method consists in reducing the pressure exteriorly of the gel. By proper regulation of temperature, ressure and the rate at which air is admitted during the liberation of the adsorbed sulfurdioxid, any desired mixture up to practically 100% sulfur-dioxid may be obtained. In all cases the equilibrium between the gas adsorbed in the gel and the same gasin the mixture .exteriorly thereof is disturbed. i For the pu ose ofillustrating a practical application 0 our invention an apparatus will be described for recovering sulfur dioxid from the exit gases of a metallurgical furnace roasting or sintering ores containing sulfur. It is to be understood, however, that the rocess is not limited to this particular app lcation, as it may be used for recover-in other gases or vapor such as carbon dioxidi ammonia, oxids of nitrogen, the vaporsof such liquids as alcohol, ether, acetone, carbon bisulfid, chloroform,gasolene,and many other gases and vapors.

- 'It is to be understood that the present invention does not depend upon a chemical combination between the adsorbent (the gel) and the adsorbed gases. On the contrary, theefliciency of the invention requires that there should be no chemical reaction between 65 the adsorbent and the adsorbed gases. This cooler 16 also act entire cooling performed by the cooler 16.

- characteristics does not mean, however, that there may not bea chemical combination of twoor more gases after they enter the 'gel.

- In the accompanying drawings, in which like referencecharacters indicate like parts:

Fi re 1 is a diagrammati view in elevation illustrating one arrangement of apparat'us for practlsing the present invention;

.Fig. 2 is a diagrammatic view in plan illustrating the apparatus shown in Fig. 1; 76

i Fig. 3 is a diagrammatic view similar to Fig. 1 showing a-modified form of the apparatus; and Fig. 4 is a diagrammatic plan view of the ap aratus shown in Fig. 3.- x

eferring to the drawingsthe ores, which may contain sulfur, for example, are

roasted or smtered in the furnace ,10 and seous products of combustion are dis- (1 through a conduit 11 to a blower 12 which forces the gases through the apparatus. From the'blower the gases may pass through a conduit 13 to a cooling tower 14,

the ga charge in which thegases are cooled to as low a temperature as can be accomplished with cooling water at river water temperatures,

'or water from other sources, This tower also serves to wash the gases free of dust, which would be objectionable in subsequent parts of the apparatus. From the'tower 14 .the gases pass through the pipe 15 to a I'cooler 16 wherein they are subjected to a standard method of refrigeration, and the temperature thereoffurther' reduced. The

cooling of the gases in the tower 14 and s to chill out or precipitate moisture from the 'gases- Preferably the gases are cooled to within a few degrees of the condensation point of the gas to be recovered, although the invention is not limited to this temperature, as the adsorption may take place at a higher temperature, but lessefliciently. Obviously, if desired, the cooling tower 14 may be omitted, and the 110 Fromthe'cooler'16 the gases pass to a manifold 17 which has branches 18, discharging into recovery towers 19, three of these towers being shown, although the invention is not limited to any specific -num ber of towers. As shown, these towel-scon- 'sist of shells having an upper head 20 and a lower head 21. In the interior of the shell and spaced from the head, 20 is a perforated head 22. A similar head 23 is spaced from the lower head 21. A series of tubes 24 have their open ends mounted in the perforations in the heads 22 and 23. Surrounding the tubesQA-and spaced from p the heads 22 and 23 is a gel 25 (having the previously described) in granular form which is capable of adsorbing the selected gas out of theproducts of combustion, that is, in the present instance, sulfur dioxid. The branch 18 discharges into the shell 19 belts the gel 25 and above the head 23, so that the gaseous products ofcombustion are passed into the gel 25. The

sulfur dioxid is adsorbed by the gel while.

the other gases pass through the same and are dischar d 1nto a pipe 26 and thence -toastack2.

The cooled mixture ofv gases is discharged into the gel until there is a trace of sulfur dioxid in the gases leaving the gel. Then ing the gel, and at the same time, admitting air through pipe 44 controlled by valve 45,

the flow of sulfur dioxid and air discharged being aided by a suction blower 46. The valve 29 in the stack being closed, the sulfur dioxid and air, the quantity of the latter being controlled by valve 45, passes along the pipe 30 to a header" 31 and thence through the pipe 32 and suction blower 46 to the place where it is used or stored. A valve 33 is provided in the pipe 30 to close this pipe when the ases are being discharged to the stack 2%. r

The heat for driving off the sulfur di-oxiid from the gel may be supplied in any desired manner. As shown, a pipe 34 extends from adjacent the outlet of the blower 12.

to the lower head 21 of the recovery tower, A valve 35 in the conduit 13 is closed so that the hot gaseous products of combustion are delivered through the plipe 34 to the re covery tower passing up rough the tubes 24 and thereby heating the gel. The ases are then discharged through a pipe 36 cading from the top head 2].. of the recovery tower to the conduit 13 at the right of valve 35,, as viewed in Fig. 1. They then pass through the cooling tower 14 and cooler 16 and may be discharged into another recovery tower where the sulfur dioxid gaswill be adsorbedby a gel in the manner already described. Thus the heat in the gasesdischarged from. the furnace is employed to drive ofl" the sulfur dioxid gas from the gel, and at the'same time this operation also acts to cool the .productsof combustion to a certain extent. The pipe 34 is connected with each'of the-recovery towers by means of a header 37 which has the branches 38,.

each leading to a tower, a valve 39 being pro 'vided in each branch so that the supply of hot gases re lated.

to the different-towers may be e sulfur dioxid gas absorbedby the el may be recovered in other ways than escribed above. For example, the .gel may be sub'ected to a partial vacuum Apparatus' or recovering the sulfur dioxid in this manner is illustrated diagrammatically in Figs. 3 and 4. In this form o apparatus the pipes 34 and 36 previously described are omitted and the recovery towers may 'beof somewhat different form. As shown this tower consists merely of a shell 19 having a gel 25 disposed therein, and spaced from the top and bottom heads 20' and 21'.

The cooled products of combustion are discharged from the cooler 16 to a header 17' and thence through a branch 18 to the tower, the sulfur dioxid gas being adsorbed in the manner already described. The other gases pass out the stack 27 the valve 29 being open and the valve 33 in the pipe 30 being closed. After the gel has adsorbed the sulfur dioxid, the valve 29 is closed and the valve 33 opened thereby putting the gel in communication with a vacuum pump 40,

charges it through a pipe 41, air being ad mitted to the shell below the gel through a valve controlled pipe 44'.

It is obvious that, instead of cooling the mixture before delivering it to the gel, the gel might be cooled, thus accomplishing the same results.

-Where the term boiling point has been Thus in recovering sulfur dioxid from the exit gases of a metallurgical furnace roasting or sintering ores containing sulfur, there is present in the exit gases some water'vapor and carbon -dioxid which, are adsorbed with the sulfur dioxid. Hence the phrase sep'a ration or recovery of a gas or vapor from a mixture of gases or vapors. is intended to cover the separation and recovery of one or unore gases or vapors from a" mixture of gases or vapors.

Although an apparatus for carrying out which draws off the sulfur dioxid and dis- "used in the, specification and claims, it is 1 intended to refer-to the boilingpoint at the method has been described specifically,

it is to be understood that the invention is not thus limited, but includes changes and modifications which come within the scope of the appended claims.

Having thus described the invention what is claimed as new and desired to be secured. by Letters Patent is 1. The method of separating and recovering a gas or vapor from a mixture of gases or vapors, consisting in passing the mixtureinto a rous body having pores substan tially o' the size of the pores in hydrated silicon'dioxid'gel, and thereafter effecting the liberation of the. gas'or vapor adsorbed in said body.

. 2. The method of separating and reoover-Q team,

ing a gas or vapor from a mixture of gases or vapors, consisting in passing the mixture into a h drated silicon dioxid gel and thereafter e ecting the liberation of the adsorbed gas or'vapor. I

3. The method of separating andrecovering a gas or vapor from a mixture of gases or vapors consisting in adsorbing the gasor vapor out of the mixture in a gel at a temperature above the boiling point of the liqueed gas or vapor-and thereafter effecting the liberation of the adsorbed, gas or vapor..

4. The method of separating and recovering a gas or vapor from a mixture of gases or vapors, consisting in cooling the mixture to a temperature above the boiling point of the liquefied gas or vapor passing the cooled mixture into a gel having ores of substantially the same size as t e pores in hydrated silicon dioxid gel and thereafter effecting the liberation of the adsorbed gas or vapor.

5. The method of separating and recovering a gas or vapor from a mixture of gases orvapors consisting in coolin the mixture to a temperature abovetheboiling point of the liquefied gas or vapor passing the cooled mixture into a gel having pores of a size to give a vaporv pressure of Water at 15 C. of from 3 to 11 milimeters of mercury and thereafter effecting the liberation of' the adsorbed gasor vapor.

6. The method of separating and recovering a gas or vapor from a mixture of gases or vapors, consisting in passing the mixture into 'a gel having pores of a size to give a vapor pressure of water'at 15 C. of from 3 to 11 millimeters of mercury to adsorb the gas or vapor out of the mixture, thev adsorption taking place at a temperature above the boiling point of the liquefied gas or vapor, and thereafter recovering the adsorbed gas or vapor from the gel.

7 The method of separating and recover ing a gas or vapor from a mixture of gases or vapors, consistingin passing the mixture into a porous body having pores of a size to give a vapor pressure of water at 15 (1.

of from 3 to 11 millimeters of mercury and thereafter effecting the liberation of the adsorbed gas or vapor.

' 8. The method of separating and recovermg a' gas 'or vapor from a mixture of gases or vapors, consisting in cooling the mixture to a temperature above the boiling point of the liquefiedgas orvapor, assing it into a gel capable of adsorbing sald gas or vapor vapor adsorbe vapor from a mixture of gases or vapors,

consisting in adsorbing the gas out of .the

.mixture in a 'gel having pores of a size turbing give a vapor pressure of water at 15 centigrade of from 3 to 11 millimeters of mercury, said adsorption taking place at a temperature above the boilin liquefied as or vapor an thereafter disthe equilibrium between the ad,- sorbed gas-in the l and the same s exteriorly of the gel to liberate the a sorbed gas or vapor.

10. The method of separating and recoveringa gas or vapor from a mixture of gases or vapors consisting in passing the mixture into a gel ca able of adsorbing said gas or vapor out o the mixture, and thereafter slightly heating the gel ,to effect the liberation of the adsorbed gas or vapor.

11. The method of separating and recovering a. gas or vapor from a mixture of gases or vapors consisting in passing the mixture-into a gel capable of adsorbing said gas or .va r out of the mixture, and thereafter sli tly heating the gel in a stream of air to e ect the liberation of the adsorbed gas or vapor. v

12. The ethod of separating and recovering a gas or vapor from a mixture of gases or vapors consisting in passing the mixture into a gel having pores of substanering a gas or vapor from a mixture of gases or vapors consisting in. passing the mixture 'into a gel having pores of a size to 've a vapor pressure of water ,at 15 C. 0 from 3 to 11 millimeters of mercu to adsorb the ,gas or vapor out ofthe' mlxture, both the mixture and gel being at temperatures above the boiling point of the liquefied gas or vapor, and thereafter recovering the ad-" sorbed as-or vapor from the gel.

14. Tie method of recovering sulfur diaoxid from a mixture of gases consisting in passing said mixture at a temperature above the boiling point of sulfur dioxid into a gel point of the capable of adsorbin the sulfur dioxid out of said mixture an thereafter recovering the sulfur dioxid from the gel.

15. The method of separating and recoverin a gas from a mixture of hot gases consisting in cooling said mixture, passing the cooled mixture into a gel capable of adsorbing said gas out of the mixture, and. thereafter heating said gel by the hot gases out-of themlxture and thereafter effecting "to'liberate the adsorbed gas.

16. The process of recovering sulfur dioxid from the gaseous products of combustion resulting from'burning sulfur containing ores,consisting in cooling the said products, passin them into a l capable of ads'orbing sul r dioxid, an heatlng said gel by 1 116 hot products of eombustion to drive v In testimony whereof we afix-our sigofi' the adsorbed sulfur dioxid.

17. In the method of separating and recovering a, gas from a'mixture of gases, the 5 step of recovering the gas previously adsorbed in a gel consisting in disturbing the equilibrium between the adsorbed in the gel and the some gas exteriorly t ere'of.

natures.

WALTERA- PATRICK.

BENJAMIN F. LOVELAGE. I 

